Electron discharge amplifier circuit



-April 16, 1935. 1. R. wElR ELECTRON DISCHARGE AMPLIFIER CIRCUIT Filed Feb. 23, l19:53

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Patented Apr. 16, 1935 UNITED STATES ELECTaoN DISCHARGE `Aiililfrrrnm CIRCUIT Irvin R.. Weir, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application February v23, v19.373, Serial No. 657,963

5 Claims.

My invention relates to electron discharge amplifier circuits which are arranged to use a plufrality of similar -electron discharge tubes. It is sometimes'd'esirable to operate such a circuit, particularly a power amplifier circuit, at a rating which is materially less than'the full tube rating yof the circuit. For example, the power demand on a four tubeA amplifier circuit may for various :reasons decrease to su'ch 'a value that it can adequately be supplied by one, two or three tubes only. Obvious economies in operation costs vwould follow such a reduction'in the number of tubes employed particularly inthe case of a'power amplifier employing modern water-cooled tubes fof la'rge capacity. Inasmuch 'as such an amplifier circuit is very carefully balanced an unnecessary tube or tubes 'cannot be removed therefrom withrout readjusting the entire circuit to preserve the balance. One object of `my invention is to provide an electron discharge amplifier circuit ine vcluding apparatus by (which the circuit 'may be 'quickly and easily converted to one of a lower .rating without affecting the balance 'or tuning of the grlid or plate circuits. Another object is the provision of an improved capacitor by the use 'o'f 'which the first mentioned object is accom- .,plishe'd.

In accordance with my invention when the capacity 'or rating of an Vamplifier circuit having tubes connected in parallel is to ybereduced I sub-'- -stitute for one 'of 'the tubes in parallel a 'double capacitor having the same electrical constantsas the tube it replaces and preferably also vsubsta-n` tially :the same 'dimensions Yas that tube. 'This capacitor which I shall vterm a 'dummy tube capacvitor is Vconstructed to fit into vand tobe secured in the socket of the tube it replaces, its three electrodes being connected in the circuitA similarly to the tube terminals. Having the same capacitance and lead inductance values as the tube it replaces the dummy tube capacitor when substituted in the circuit does not 'disturb the balance or tuning of the circuits. Also by constructing the dummy tube capacitor to correspond in form with` a tube l, the capacitor is better adapted for use where the space available is limited to that required by a tube.

My invention will be better understood from the following description taken in connection with the accompanying drawing, and its scope will be pointed `out in the appended claims.

Fig. 1 is a cross-sectional view showing the dummy tube capacitor comprising one feature of my invention; Fig. 2 is a circuit diagram of a Well-known form of power amplier; Fig. 3 is a similar circuit diagram of the same powerampli- Ifier but embodying another feature of my invention; and Figs. 4 and 5 are circuit diagrams of modified-forms of power amplifier also embodying my invention.

Referring first to the dummy tube capacitor C shown in Fig. 1, the Water jacket I together with vthe inlet and outlet pipes 2 and 3 for the -c`o`oling 'water and the securing `screws It are parts which are regularly employed for supporting `and cooling the power amplifier tubes such as are employed in power amplifiers of relatively large capacity. The dummy tube capacitor which I have vdevised is constructed and arranged to be substituted for or to replace an operative amplifier tube in the event that the tube is not re quired. The dummy tube capacitor as shown in Fig. l .comprises "the .base member "Blwhose form is similar to the corresponding member 'of the amplifier tube for which it is substituted and hence fits into the water jacket I where it may ybe clamped in place by the tube clamping screws '4. Secured to base S is the dummy plate member l which is provided with passages 8 there# throughfor the circulation of lcooling Water. Sec'ured also to the base 6 isthehollow support 9 of insulating material'such as glass or quartz to whose upper end is secured the dummy grid 'member I0. This'member is in the YformA of an inverted cup which surrounds the dummy plate member l but is spaced therefrom and the space is filled with a suitable solid dielectric material such for example as sulphur. By this construction the 4grid member II) is suitably insulated against the high potentialof the plate member 'I and the capacitance between those members i's the Vsame as the grid-plate capacitance in an amplifier tube for which the capacitor is substituted. Dummy cathode member I2 having a cup-shape form is supported on the grid member III by means of the insulator I3. This member I2 surrounds the grid member Ill and is spaced therefrom, the dielectric between these members being air. The capacitance between members I8 and I2 is the same as the grid-cathode capacitance in the amplifier tube for which the dummy tubecapacitor is substituted. Suitable terminals I4, I5 and IS are provided for members l, I Il and I2 respectively for the vconvenient connection of those members in the'circuit when `the capacitor is substituted lfor an amplifier tube. Inasmuch as the'space allotted to the apparatus of a power tube amplifier l often 4is limited to the absolutenecessities thereof the dummy tube capacitor which vIhave devised is the other tube.

constructed to conform substantially to the dimensions oi an amplier tube for which it is to be substituted thereby facilitating its use in the amplifier circuit.

In order better to understand my invention I have shown in Fig. 2 a well-known form of pushpull power amplifier circuit i9 embodying two ampliier tubes connected in paraliel in each side of the push-pull circuit. As shown in this figure the input circuit iii connects through the input transformer 2| with the grids of ampliiier tubes 22 and Z3 in one side ofthe push-pull circuit and with the grids of the ampliiier tubes 24 and 25 in the other side thereof. The plates of the ampliiier tubes connect through the output transformer 26 with the output circuit 2 and with the source of supply 28 of plate voltage. The push-pull circuit is shown provided with various tuning circuits which being Well known in the art will not be described. With allA four tubesv 22.-*25 inclusive in place the fourtube circuit shown in Fig. 2 is adapted for full capacity use.

In Fig. 3 I have shown the same circuit modified by the substitution of a dummy tube capacitor such as shown in Fig. l for each of two of the `amplifier tubes thereby reducing the capacity of the ampliiier from a four-tube circuit to a twotube circuit. Thus in Fig. 3 it will be seen that amplifier tubes 22 and 25 have been replaced by the dummy tube capacitors C. Since the gridplate and the grid-cathode capacitance and inductance of the dummy tube capacitor is the same respectively as the grid-plate and the gridcathode capacitance and inductance of the amplifier tube which it replaces, the substitution of the dummy capacitors in the circuit does not disturb the carefully balanced and tuned condition of the circuits. Moreover since thev dummy tube capacitor is constructed to fit the amplifier tube holder the exchange of a tube for a capacitor may be made quickly and conveniently, there being no circuit adjustments necessary except that of vconnecting the terminals of the capacitor to the circuit terminals to which the tube terminals previously connected. Likewise a tube may be substituted for a dummy tube capacitor with equal speed and convenience.

The modified form of my invention shown in Fig. 4 is similar to that of Fig. 3 except that each side of the push-pull circuit is adapted to include one amplifier tube, instead of two. As i1- lustrated by Fig. 4, one side of the circuit contains amplifier tube 39; in the other side of the circuit the tube has been replaced by the dummy tube capacitor C.

The modified form shown by Fig. is a single circuit 29 which is adapted to employ two amplifier tubes in parallel.v The circuit is represented as including the single amplifier tube 3B and the dummy tube capacitor C substituted for The input circuit -is shown as including the transformer 3i and the output circuit as including the transformer 32, the plate voltage in this case being shown as applied by the battery 33.

The dummy tube capacitor not only is useful to reduce the power of the ampliiier circuit but is useful in the construction of an amplifier circuit to balance the circuit so that a push-pull load may be taken from it. The power required from an amplifier circuit may be such that a single ampliiier tube is sufficient but if a transmission line loadmust be taken from the ampliiier the use of a dummy tube capacitor solves the problem of balance of that load.

I have chosen the particular embodiments described above as illustrative of my invention and it will be apparent that various other modications may be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. An electron discharge amplier circuit constructed and arranged to employ a plurality of electron discharge tubes having the same electrical characteristics and connected in circuit with each other, an operative electron discharge tube and a dummy tube capacitor connected in said circuit in parallel with each other, said dummy tube capacitor having its electrodes spaced by a solid dielectric and having the same electrical characteristics as said operative discharge tube.

2. An electron discharge amplifier circuit having portions operative respectively on the positive and the negative half waves of the alternating current supply, each of said portions being constructed and arranged to employ a plurality of electron discharge tubes having the same electrical characteristics and connected in parallel with each other, an operative electron discharge tube and a dummy tube capacitor connected in each of said portions in parallel with each other, said dummy tube capacitors having the form of said operative tubes and provided with solid dielectrics at atmospheric pressure and having the same electrical characteristics as the discharge tube with which they` connect in parallel.

3. A dummy tube capacitor constructed to replace anelectron discharge tube in an amplifier circuit and having the same electrical constants and substantially the same dimensions as said tube, said dummy tube capacitor comprising a dummy plate member, a dummy grid member surrounding said plate member and separated therefrom by a solid dielectric, an outer dummy cathode member spaced from said plate member, and a base member connected with said plate member and constructed to fit the socket of said sube.

4. A dummy tube capacitor constructed to replace an electron discharge tube in an amplifier circuit comprising a central dummy plate member, an inverted cup-like dummy grid member enclosing the upper end of said plate member, a solid dielectric therebetween, an inverted cuplike dummy cathode member supported over and spaced from said grid member, and a base arranged to seat in and to be secured to the tube socket.

5. A dummy tube capacitor constructed to replace a water cooled electron discharge tube in a power ampliiier circuit and to have the same electrical constants and substantially the same dimensions as said tube comprising a core-like dummy plate member, a base member secured thereto and constructed to fit into the tube socket, an inverted cup-like dummy grid member enclosing the upper end of said plate member, sulphur dielectric therebetween, a glass enclosing member secured at opposite ends respectivelyto said grid and base members, and an inverted cup-like dummy cathode member secured over said grid member and spaced therefrom by an air dielectric.

IRVIN R. WEIR.' l l 

